Counter-output apparatus of the above-noted general type finds application in various industrial endeavors, a principal use thereof being found in controlling manufacturing processes. In such use, input signals generated on completion of each of a preselected number of successive operations on a workpiece are applied to the apparatus and are accumulated and an output signal is then generated on accumulation in such preselected number for effecting transferral of the workpiece to a succeeding work station, or other change in activity. In accommodating this practice, the counter apparatus need have various functional capabilities. It is required to be operator-presettable to yield such output signal upon occurrence of such preselected number of operations (presetting function). The apparatus need count individual such operations (accumulate function), have the capability of retaining counts (count latch function), provide an output indication of count accumulation in preset amount (preset count output function) and have the capability of returning to its original condition (reset function).
Exemplary of diverse prior art apparatus of this type are devices shown in U.S. Pat. Nos. 1,908,626 (Ford) and 3,489,175 (Loveless et al.). The Ford patent sets forth a mechanism which accommodates the foregoing functions, however, with various operational limitations. The mechanism is responsive only to translatory mechanical input signals in its accumulate function. It achieves its presetting function only upon disassembly of releasably secured count presetting components. In its preset count output function, the Ford apparatus effects mechanical operation of an apparatus-contained electrical switch and does not depict structure providing desirable fluid pressure output signals external to the apparatus. It includes a reset mechanism operative to clear the apparatus to original preset condition solely in response to mechanical activity and then simultaneously with attainment of such preset count.
The Loveless et al. patent discloses apparatus which is desirably responsive to fluid pressure pulse input in its accumulate function and is count-presettable without component disassembly. However, the mechanism thereof achieves its count latch function by dependence upon such fluid pressure pulse input. In its preset count output function, this apparatus conveys its input pulse to an output port and thereby has its output signal limited in pressure characteristic. In its reset function, the Loveless et al. apparatus releases such latch in response to a change in differential fluid pressure across its latch piston coincidental with the last pulse in the counting sequence. While mechanically resettable at any time, the apparatus is not fluid pressure resettable at user option at any time during or after the count sequence.